You are asking two things so far as I can tell. First is why is it wrong. The second is how is it cultural appropriation. The first question has to answers, the second has one.
1st question answers.
Part 1.
My opinion is that it's not wrong. Infact, this is a good thing. A person from a different culture is wearing clothing that is styled from another culture. She has been enriched and will also spread that around.
Part 2.
From the perspective of a SJW this is bad. The reason is this.
https://www.npr.org/sections/codesw...ultural-appropriation-is-in-fact-indefensible
Asians, specifically the Chinese have been the victims of White oppression as all non-white groups have been in the past. White - oppressor wearing cloths from a group of people they have oppressed.
2nd question.
It's cultural appropriation because she is white wearing clothes from a culture that whites have oppressed.